[SPEC] POC of Rayon / wasm-utils on the dApp

# Overview
The wasm-utils and arkworks tools can be built with parallelization using `rayon`. This may also now be available in the chrome browser and could potentially lead to large speedups in ZKP generation and note generation.

## Tasks
- [ ] A proof of concept using: https://github.com/GoogleChromeLabs/wasm-bindgen-rayon.
- [ ] Spec out some tasks relevant for full integration.
